1. Field of the Invention
The present invention relates to a vehicle power steering control apparatus that appropriately controls an assist torque for a steering torque of a driver, when there is an obstacle ahead.
2. Description of Related Art
There have recently been proposed various vehicular driving support apparatuses for detecting an obstacle ahead of a subject vehicle so as to avoid a collision against the obstacle ahead. In order to avoid the collision against the obstacle ahead, a braking operation and turning operation are generally executed. As a technique of avoiding the collision with the obstacle ahead by the turning operation, Japanese Patent Application Laid-Open (JP-A) No. 2009-137344 (hereinafter referred to as JP-A No. 2009-137344) describes a steering force control apparatus, for example. When an object is detected ahead of a vehicle, and a degree of risk (inverse number of an allowance time) is a first risk degree or higher, a first correction gain to a base assist torque based upon a steering operation state by a driver and a second correction gain to a behavior-stabilization assist torque based upon a vehicle behavior are increased, and then, a total assist torque is calculated in order that the driver can easily make a steering operation for avoiding the collision with a low steering toque.
Under the condition where the driver makes the steering operation for avoiding the obstacle ahead of the vehicle, the vehicle may enter an unstable and dangerous situation after the driver makes the steering operation for avoiding the obstacle that is a subject to be avoided, because the steering operation for avoiding the collision is excessive. According to the technique described in JP-A No. 2009-137344, the vehicle behavior described above is suppressed by the behavior-stabilization assist torque based upon the vehicle behavior. However, the correction is made only in an increasing region of the assist torque. Therefore, an excessive steering by the driver cannot be prevented, whereby an effective measure cannot be taken.